(1) Field of the Invention
The present invention relates to a thermoplastic resin composition having excellent mechanical toughness, particularly impact resistance and heat resistance of molded articles made therefrom. This composition of the present invention can be widely utilized as materials for electrical and electronic parts, automobile parts and the like.
(2) Description of the Prior Art
Engineering plastics are excellent in heat resistance, modulus elasticity, mechanical strength, and impact resistance, and in recent years, they are known as a substitute for metallic materials. In addition, engineering plastics have a variety of characteristics such as light weight, excellent moldability and coloration, and can be widely used as indispensable industrial materials for structural and machinery parts of automobiles, electrical and electronic products, and precision machinery and tools.
These engineering plastics are divded broadly into the following two categories.
Engineering plastics for popular use:
polyamides (PA); aromatic polyesters such as polyethylene terephthalates (PET) and polybutylene terephthalates (PBT); PA0 polyphenylene oxides (PPO); polyacetals (POM); PA0 polycarbonates (PC); ABS resins. PA0 polyphenylene sulfides (PPS); polyarylates (PAR); PA0 polyether ether ketone resins (PEEK); liquid crystal polymers (LCP).
Heat-resistant super engineering plastics:
With regard to these engineering plastics, noncrystalline plastics such as PC, PPO, ABS and the like are somewhat poor in solvent resistance and flowability in comparison with crystalline plastics such as aromatic polyesters, PPS, LCP and the like.
Crystalline plastics are excellent in heat resistance, modulus of elasticity, but have the disadvantages that they are by nature brittle and anisotropic. For example, aromatic polyester resins are excellent in mechanical strength, but poor in impact resistance, especially in notched Izod impact strength.
For the purpose of improving the impact resistance of aromatic polyester resins, a method has been proposed in which a rubber-like polymer is blended with the resins. However, when a rubber-like polymer is mixed in a relatively large amount to improve the impact resistance, the heat resistance of the resulting mixture which is a feature of the aromatic polyester resins is impaired unpreferably, because such a rubber-like polymer as an effective modifier for impact resistance has a glass transition temperature below ambient temperature.
In the recent years, some methods for solving these problems are disclosed. For example, in Japanese Patent Unexamined Publication Nos. 52-32045 and 53-117049, there are described examples using a copolymer of an .alpha.-olefin with an .alpha., .beta.-unsaturated glycidyl ester to be blended in order to improve the heat resistance. Japanese Patent Unexamined Publication No. 60-40154 discloses also an improved method wherein a modified polymer obtained by grafting a monomer such as .alpha., .beta.-unsaturated glycidyl esters on to a copolymer of an .alpha.-olefin with a nonconjugated diene. These approaches have been solving these problems to a certain extent.
Further, PA are excellent in moldability, heat resistance, abrasion resistance and solvent resistance, but they are poor in dimensional stability because they are highly hygroscopic.
As for PPO resins, they are excellent in mechanical and electrical properties, heat resistance and dimensional stability, but poor in moldability, oil resistance and impact resistance.
PC resins are excellent in heat resistance, mechanical strength, impact resistance, but poor in chemical resistance , and POM resins are excellent in dimensional stability and mechanical properties, but poor in impact resistance.
As for ABS resins, they are excellent in impact strength, but poor in chemical resistance.
Furthermore, PPS resins are excellent in heat resistance and flame resistance, but poor in ductility.
PAR and LPC are excellent in heat resistance, but poor in impact resistance.
Various attempts have been made to obviate these drawbacks. Among them, resin compositions containing the aforesaid modifier, composite plastics with filler and glass fiber, and polymer alloys made from several kinds of engineering plastics have been proposed. However, the heat resistance is deteriorated in the compositions containing a rubber-like modifier, and impact resistance is impaired in the composite plastics containing fiber or filler, and the features of the engineering plastics are spoiled more or less in the polymer alloy.